Notes
1716 Inorganic Chemistry, Vol. 14, No. 7 , I975 S4 00 for photocopy or $2 50 for microfiche, referring to code number
H t CH,OH
-+
k j = 1.6 X l o 6 1 W - l sec-’
C H , O H + H,
41C30394H
References and Notes
sec-’
R . A . Kolodny, T. L. Morris, and R. C . Taylor, J . Cheni. Soc.. Daiton Tram., 328 (1973). ( 2 ) J. V . Quagliano. A . K. Benerjee. V . L. Goedken. and L.M . Vallarino. (I)
(3)
(4) (5) (6) (7) (8) (9) (IO) (1 I ) ( I 2)
(I 3) (14) ( 1 5)
(16) (17) (18)
J . Am. Chem. Soc.. 92. 482 (1970). C. Ercolani. J . V. Quagliano. and L Li. Vallarino, Inorg. Chin?. Aero, 3, 421 (1969). W . L’ Dahlhoff. T R . Dick. and S. M Nelson, J . Chem. Sac. A ,2919 (1969). R . L. Carlin, Transition Mer. Chem., 1, 1 ( 1 9 6 5 ) . B. 5 , Figgis and J . Lewis, Prog. Inorg. Chem.. 6 . 37 (1964). D . Berglund and D. W. Meek. Inorg. Chenz., 8, 2602 (1969). B. B. Garrett. V L Goedken. and J . \’. Quagliano, J . Ani Chei77 Soc., 92, 489 (1970). D. \1. L. Goodgame and h l . Goodgeme, Inorg. Chem.. 4. 139 (1965). A . B. P. Lever a n d S . M.Nelson, J C h e m Soc. A , 859 (1966). F. A . Cotton, D. M.L . Goodgame, and tvl. Goodgame, J . A m .C h e m Soc., 83. 4690 (1961). Suppiementary material. A . B. P. Lever. “Inorganic Electronic Speclroicopy“, Elsevier, 4 m sterdam. 1968. pp 225-232. F. Sorm and L . Sediv!. Coiiect. Czech. Chenz. Comniun., 13, 289 (1948). D. H. Brown, K . P. Forrest, R. H . Nuttail, and D. LV. A . Sharp, J Chrm. Sue. A , 2 I46 ( 1 9 6 8 ) . L. LV. Daasch and D. C. Smith. A n a / . Chem.. 23, 853 (1951) M . A U’einer. J . Organonzer. Chenz., 23, C20 (1970). Chemical shifts in D2O are reported downheld from sodium 2,2-dimethyi-2-silacqclopentane-5-julfonate ‘1s internal standard.
Contribution from the Chemistry Department.
Kuclear Research Centre-Negev, Beer-Sheva, Israel
Kinetics of Complexation of Copper(1) Ions with Maleate and Fumarate in Aqueous Solutions. A Pulse Radiolytic Study D . Meyerstein A I C 40 5 7 8 W
Received August 15, 1974
Copper(1) ions form relatively stable complexes with organic compounds containing unsaturated carbon-carbon bonds.l.2 These complexes have typical absorption bands in the near-uv region.l.2 It seemed of interest to measure the kinetics of formation of such complexes. Thus, information concerning the rate of ligand exchange of copper(1) ions could be obtained. No data concerning the specific rate of ligand exchange of copper(1) have been reported to the best of our knowledge, though very high rates would seem reasonable for a monovalent dl0 cation.
Results and Discussion The pulse radiolytic technique was chosen for this study.3 (The experimental procedure has been described elsewhere in detail.4) Nitrous oxide saturated solutions containing 1.O X 10-2 M CuSO4, 1.OM methanol, and 1.0 X 10-5-1.0 X 10-3 M of furmaric or maleic acid at pH 3.65 f 0.05 were irradiated by 2.5 X 1019 eV/1. pulse. Reactions 1-10 might occur under H,O e&
2 eaq-, H,OH, H,,H,O, + N,O + H,O+ OH + N, -+
k , = 3.3 x sec-l
eaq- T Cuaqz+-+ Cuaq+ OH
+ CH,OH
+
CH,OH
k , = 8.7 X sec-’
+ H,O
k , -4.6 X
sec-’
C H 2 0 H + CuaqZc--L Cuaq+
(5 )
k , = 5 x l o 8 :W’
H t Cuaqz- + CuaqL + H,O+ CH,O
(6)
k , = 1.1 X l o 8 ’VI-’ sec-l
Cuaq- - cis- or rrans-HOOCCH=CHCOOH
(7)
k
& k
[ HOOCCH=CHCOOH]* cu .H cis- or rrans-HOOCCH=CHCOOH --t HOOCCH,CHCOOH k , = 6 x l o * and l o 8 &!K’sec-’, respectively7
(8)
-
+
C H , OH HOCCH=CHCOOH k,, = ?
--t
(9)
HOOCH(CH,OH)CHCOOH
(10)
these conditions. (The yields of the radicals for eq 1 are3 Ge,%, = 2.65, GOH = 2.65, GH = 0.6, GH:Q = 0.75, and GH?= 0.45 where G is defined as the number of molecules of product formed by absorption of 100 eV by the sample). Reaction 9 competes with reactions 6 and 5 for the hydrogen atoms, but even at the highest concentration of the unsaturated acid used, 1 X 10-3 M ,less than 1S% of the H atoms react via reaction 9 . As the hydrogen atom yield is about 10% of the total radical yield, the maximal effect of reaction 9 is to decrease the &(I) concentration by 2%. Reaction 10 was found by blank experiments carried out in the absence of Cu2+ to be slow relative to reaction 7 and can be neglected. Therefore all the radicals formed under the experimental conditions reduce CUaq’+ to Cuaq+, and G(Cuaq+) = 5.85. (A somewhat higher yield is plausible due to the high solute concentrations.8) The formation of Cuaq+ends within less than 2 ysec. The absorption spectra of the products formed by the pulse were measured 50 ysec after the pulse and were stable for several minutes. The spectra are shown in Figure 1 with h x ( c o p p e r ( I ) maleate) 345 f 10 nm. Emax 2800 f 500 M-1 cm-I, and Xmax(copper(I)fumarate) 335 f 10 nm, t m a x 3000 f 500 M-1 cm-1. (In Figure 1 the observed optical densities, OD: and the molar absorption coefficients, t, calculated from OD: the pulse intensity, and the total radical yield are shown. The figures given above are higher by 10% due to the fact that in solutions containing 1 X 10-3 M unsaturated carboxylic acid 10% of the Cu(1) is uncomplexed; see below.) No stable products having absorption in the 300-500 nm range were observed when either CUaqZ+ or the unsaturated carboxylic acid were omitted from the solution or when malonic acid was used instead of the unsaturated carboxylic acid. The observed spectra are similar to those reported in the literature for the same complexes at p H 0 . 2 The small shifts in Xmax and the larger Emax observed in this study are attributed to the partial acid dissociation of the carboxylic groups at pH 3.65. The kinetics of formation of the absorption due to the Cu(1) complex always obeyed a pseudo-first-order rate law. The observed specific rates of reaction, k , are plotted against the unsaturated carboxylic acid concentration, C. in Figure 2. From the intercept and the slope of the straight lines obtained ks and k-s can be calculated. ( k = ksC + k-s is predicted from the suggested mechanism.9) Thus for maleic acid ks = (2.0 4 0.4) X 109 M-1 sec-1, k-s = (1.8 f 0.4) X 105 sec-1, and Ks = ks/k-s = (1.1 f 0.3) X lo4 k - l and for fumaric acid k~ = (1.7 f 0.4)X lo9 M-1 sec 1 , k-8 = (2.4 f 0.4) X 105 sec-1, and Ks = (7.1 f 2.0) X 103 M-1 are obtained. The high specific rates of reaction 8 are in agreement with the expected rates of water exchange of Cuaq+ ions. The stability constants of the complexes were also calculated from the effect of the unsaturated carboxylic acid concentration on the yield of the complex as measured by the optical density
Inorganic Chemistry, Vol. 14, No. 7, 1975 1717
Notes
the complex, ODT, from K8 and the measured OD in solutions for which C = 7 X 10-4 M , using the equation ODT = OD( 1 4- &C)/Ksc. Using the value of ODT K8 was calculated for all other concentrations by applying the equation
0.D
0.075
Ka =
2000
OD 1 O D -~OD C
The average of these values of Ks was used for a new calculation until a self-consistent value was obtained.] The average values for K8 thus obtained, (1.3 f 0.2) X 1 0 4 and (9.0 f 2.0) X 103 M-1, for maleic and fumaric acid, respectively, are in good agreement with those obtained from the kinetic study.
005 0
1000 0.025
Acknowledgment. The author wishes to thank Mr. Y . Ogdan from the linear accelerator group of the Hebrew University of Jerusalem for his help with keeping up and running the electronic equipment. Registry No. Copper(1) fumarate, 54964-69-1 ; copper(1) maleate,
55028-63-2. Rgure 1. Absorption spectra of the complexes, measured 50 Msec after the pulse, with the solution composition of 1 X lo-' M CuSO, and 1.0 M methanol (N,O saturation and pH 3.65 i 0.05): M fumaric acid. M maleic acid; A, 1 X 0, 1 x
References and Notes ( 1 ) R. M. Keefer, L. J. Andrews, and R. E. Kepner, J . A m . Chem. Soc , 71, 2381, 3906 (1949). (2) J. K. Hurst and R. H. Lane, J . Am. Chem. SOC.,95, 1703 (1973). (3) M. S. Matheson and L. M. Dorfman, "Pulse Radiolysis", MIT Press,
Cambridge, Mass., 1969. (4) D. Meyerstein and W. A. Mulac, J. Phys. Chem., 72,784 (1968); fnorg. Chem., 9, 1762 (1970); Y . Hare1 and D. Meyerstein, J . Am. Chem. Soc., 96, 2720 (1974).
( 5 ) M. Anbar and P. Neta, Int. J . A p p l . Radiat. fsot., 18, 493 (1967); M. Anbar, M. Rambener, and A. B. Ross, Natl. Stand. Ref Data Ser., Natl. Bur. Stand., No. 43. (6) H. Cohen and D. Meyerstein, J. Am. Chem. Soc., 94, 6944 (1972). (7) P. Neta and R. H . Schuler, Radiat. Res., 47, 612 (1971). (8) G. E. Adams, J. W. Boag, and B. D. Michael. Trans. Faraday Soc., 61.
2.0
492 (1965).
I;f;
(9) The reviewers have requested the derivation of the rate law. The reaction
I 0
I
I
I
1.0
2.0
3 .O
I
I
c
Figure 2. Dependence of the observed specific rates of reaction,
acid; A, maleic acid. Table I. Stability Constants of Copper(1) with Maleic and Fumaric Acidsa [Cl,M
OD
1.0 x 10-5 2.0 x 10-5
o.oioo
3.0 X lo-'
0.0240 0.0306 0.0401
4.0 X 6.0 X 7.0 x 10-5
0.0200
10-4~,,~-*
1.3 1.5 1.5 1.4
1.4
8.0 X 1.0 X
0.0438
1.3
0.0481
1.2
1.5 X lo-, 2.0 X lo-, 4.0 X lo',
0.0543 0.0621 0.0677 0.0759
1.2
7.0 X lo-,
1.3
0.9 1.1 Av 1.3
k
A+B&C k
X*104 M
k, o n the unsaturated carboxylic acid concentration. Aqueous solutions containing 1 X 10'' M CuSO, and 1 .OM methanol (pH 3.65 i 0.05 and N,O saturation) at 22 i 2" were used: 0 , fumaric
Maleic acid
studied can be summed up as
-8
where [C]r=o = 0, [AIM = Ao, and [B] >> AO, Therefore d[C]/dr = d [ A l / d t = k B [ A ] [ B ] - k - ~ [ C ] =ks[A][B] - k - 8 ( A o - [.4]) = (kx[B] + k-a)[A] - k-xAO. Integration of this equation yields -In { ( k s [ R ]+ k-s)(A] - k-8A0) = (ks[B] + k-x)f + constant. I f the equilibrium concentrations are A" and C", respectively, then kxA"[B] = k - x P = k-8(Ao - A"); k-8Ao = (ks[B] + k-x)A". Therefore -In ((ks[B] + k-B)[A] - (ks[B] -t k-8)A") = (ks[B] + k-8)t + constant or -In ([A] - A " ) = (ks[B] + k-8)f + constant. Thus the observed rate constant k equals k8[B] + k-8.
Fumaric acid
~O-~K,,M-~ 10.0 9.6 0.0200 9.5 0.0262 10.0 0.0333 9.5 0.0345 8.5 0.0378 8.8 0.0414 8.3 0.0488 7.9 0.0567 7.9 0.0718 9.1 0.0783 8.5 OD
0.0089 0.0147
Av
9.0
a All solutions were N,O saturated and contained 1 X lO-'M CuSO, and 1.OM methanol a t pH 3.65 i 0.05;OD measurements were taken a t 350 n m , 50 Msec after the end of the pulse. Accuracy of K , is i 2 0 % . [C] is the concentration of the unsaturated carboxylic acid, at 22 i 2" and p = 0.04.
a t 350 nm. The results a r e summarized in Table I. [The calculation was carried out by assuming the value obtained for Ks in the kinetic runs, and calculating the optical density for a solution in which 100% of the Cu(1) formed appears in
Contribution from the Department of Chemistry, Texas A&M University, College Station, Texas 77843
Crown Ethers in Inorganic Chemistry. Preparation and Characterization of the Group 6 Pentacarbonyl Hydroxides and Fluorides John L. Cihonski' and Robert A. Levenson'
Received October 21. I974
AIC40724Y
Crown ethers have been employed recently in organic chemistry to dissolve inorganic salts in nonpolar media and to thereby promote reactions that would either occur only slowly or not a t all.2-5 As yet, we know of no reports of their use as an aid in the synthesis of transition metal complexes. Depending upon the ring size of the crown ether, different cationic species may be complexed with varying degrees of efficiency.233 Also, increasing the size and number of organic
